DHCP Lease
Time-limited assignment of an IP address from a DHCP server to a client, renewed periodically until it expires.
A DHCP lease is the time-limited assignment of an IP address (plus subnet mask, gateway and DNS servers) from a DHCP server to a client. The lease is created at the end of the DORA exchange, when the server sends DHCPACK, and it carries a lease time together with two renewal timers: T1 (typically 50% of the lease) and T2 (typically 87.5%).
At T1 the client tries to renew with the original server using a unicast DHCPREQUEST. If that fails, at T2 it rebinds by broadcasting to any reachable DHCP server. If neither succeeds before expiration, the client must release the address and restart the DORA process from scratch. Returning the address explicitly via DHCPRELEASE lets the server put it back into the pool immediately. Lease times are a policy choice: home networks often use hours to a day, enterprise networks may use days, and short leases (minutes) are common in high-churn environments such as guest Wi-Fi. MAC-based reservations are layered on top to give specific devices a stable private IP from within the same pool.
Key Points
- Time-limited assignment confirmed by
DHCPACKat the end of DORA - Renewal timers T1 (~50%) and T2 (~87.5%) of the total lease
- Renewal is unicast to the original server; rebinding is broadcast
- Expiration without renewal forces a fresh DORA exchange
- Short leases suit high-churn networks; long leases suit stable ones
- Reservations bind a MAC address to a fixed IP inside the same pool